During manufacture of dialyzers, the correct and sufficient sterilization thereof is important to safely kill microorganisms having detrimental effects for a patient, such as bacteria, viruses, fungi and the like.
In accordance with the European Standard (EN) 556, an object can be considered to be sterile when the theoretical value of no more than one living microorganism is present in 1×106 sterilized units of the final product. For sufficient sterility of dialyzers for extracorporeal blood treatments, therefore e.g. the presence of viable organisms has to be reduced by 6 levels to a sterilization target of the Sterilization Assurance Level (SAL) 10−6 or SAL 10-6.
Common methods for sterilizing dialyzers are based, for example, on the utilization or use of gamma radiation, electron radiation, ethylene oxide (EtO/EO) and superheated steam. In said methods, radiation, heat and toxicity have a killing effect on microorganisms.
All of the afore known sterilization methods for dialyzers have specific drawbacks, however.
Gamma sterilization, for example, depends on a radioactive isotope (60Co or 137Cs). Procuring the latter is difficult, transport thereof is complicated and an appropriate waste disposal site is required. Gamma radiation systems in addition require very complex measures for shielding the radioactive radiation. Moreover, the radiation process takes several hours due to the low dose rate intrinsic to its operating principle.
Although sterilization by electron radiation requires no radioactive isotope, it requires complex shielding measures due to the deceleration radiation occurring during the process analogously to gamma sterilization. Moreover, for generating electron beams complicated and thus expensive accelerators are necessary to obtain the required penetration depth which for electron beams is substantially lower than for gamma rays.
The ethylene oxide used for EtO sterilization in turn is a strong protoplasmic toxin, it is carcinogenic, mutagenic, allergenic and chemically irritative and consequently highly toxic, cancer-causing and, in addition, highly explosive in a gas mixture with air having an ignition point of only 40°. Thus, it constitutes a considerable risk. Removing the ethylene oxide from the dialyzer after accomplished sterilization is rather time-consuming.
The generation of superheated steam required for superheated steam sterilization finally is energy-consuming and, due to the high temperatures, is a considerable load for the components of the dialyzer. In order to be able to apply superheated steam sterilization, the dialyzer further has to meet specific requirements in terms of design.
Against this background, there is a demand for alternative options for sterilizing especially dialyzers for extracorporeal blood treatments.